Normal Map + Micro Displacement = Bug?
It seems as of version 2.79, displacement node, Adaptive subdivision (experimental mode) cannot be combined with normal map node. Workaround for now is either using only bump map or switching off the adaptive option inside of subdivision modifier. 

This bug is not noticeable when using simple plane: (probably here tangent space is same as object space)


In case of a sphere, shading artefacts appear when combining Normal Map and Adaptive Displacement


Unfortunately I now have the file in version 2.8 only
http://gofile.me/2mjhf/tn9buuTmU

Node setup in 2.8:


Correct me if I am wrong, but it seems like developers were aware of this bug and changed it in the upcoming version 2.8. Since that is around the corner I can live with the 2 above mentioned workaround in 2.79 until then.

Thanks